Dereck Rodriguez is the perfect example of giving a young player an opportunity, and see what happens. I hear the "he isn't ready" mantra so often, from team reps and from fans and on these boards. Some will be. Dereck was, and way before all the "experts", including ours, said he was. He took the opportunity and he was ready. The Giants are the winners, and the Twins are the big losers.
Dereck was in that odd position of being a player that switched to pitching and was getting older and still on the farm and the two combined with his ability to be a free agent pushed him to leave the Twins. The Twins didn't take the 40-man chance that they had to do because they felt he was still behind others (Chargois, Curtis et al). minor league service time doesn't compensate a team for time a player spends recovering from an injury or, perhaps, doing a position change. At some point, after being in the minors for x-many years, playing for one organization or another is pretty much the same.
And a team really isn't going to overpay a minor league guy to keep him in the minors (not on the 40-man) if they are still in prospect mode.
If anything, the handling of Rodriguez showed that the Twins still are a bit subdued on advancing players too fast, or just advancing players and getting a look and evaluating them according to that advancement.